Cannulae with introducer stylets are used for introduction into various organs of the body to introduce or withdraw fluids. One such use is a retrograde coronary sinus perfusion cannulae used in connection with open heart surgery. The cannula itself may be flexible, but the stylet within the cannula has sufficient rigidity that the combined cannula and stylet may be manipulated by a handle on the cannula to project into the selected organ of the body. Usually the stylet is withdrawn from the cannula after the successful introduction.
It is often desirable to place these types of flexible cannulae in friable vessels of the body having tortuous paths. A stylet having essentially uniform characteristics over the entire length of the cannula has typically been used. This conflicts with the necessity for the person placing the device to have a relatively stiff guiding stylet to locate the tip of the catheter near the desired opening or ostium, yet also embody flexibility to be self-guiding and atraumatic within vessels. By having two distinctly different types of construction or material characteristics along the stylet, each section can be appropriately tailored to meet these two criteria.
Retrograde coronary sinus perfusion cannulae in particular would benefit from an introducer stylet having a stiff proximal end and a flexible shape-retaining distal end. This type of cannula must be introduced through a small hole formed in the right atrium, and then moved through the interior of the atrium into coronary sinus ostium. The latter movement must be essentially blind, with the surgeon having to function by feel through the back heart wall. It would therefore be highly desirable to be supplied with an introducer stylet that may be bent at the distal end into a curve that suits the size of the heart, and yet possess a relatively stiff distal end that may be manipulated to advantage by the surgeon.
The present invention is directed to an improved removable cannula introducer in which there is a variable stiffness embodied in the length of the introducer, from a relatively stiff proximal portion to a more flexible yet shape-retaining distal end. While the overall length of the cannula and stylet may vary for different applications, an appropriate example is a 12" length not including the manipulative handle that is attached to the stylet. The invention is also directed to a retrograde coronary sinus perfusion cannula that employs such an introducer. The cannula comprises an elongated flexible tube with a central perfusion lumen and an integral side lumen for pressure monitoring. An inflatable cuff encircles the tube adjacent to the distal end thereof, and may be either self-inflating through communication with the central lumen or air-inflatable through a second side lumen. The introducer is assembled to the cannula by insertion from the proximal end into the central lumen.
An object of the invention is to provide a reinforcing introducer stylet for a cannula, the stylet having a handle to be used by the physician to manipulate the introduction. Another object of the present invention is to provide, for a relatively flexible cannula, a removable introducer stylet that provides proximal control stiffness and distal flexibility properly to install the cannula prior to removal of the introducer stylet.
Other objects and features of the invention will be apparent in the following description and claims in which the principles of the invention are set forth together with details to enable persons skilled in the art to apply the principles and techniques of the invention, all in connection with the best mode presently contemplated for the invention.